The aim of the proposal is to study the control of the circulatory system by neural pathways in normal and congestive heart failure animals. These studies are divided into work with anesthetized and work with conscious, instrumented animals. The extent to which cardiovascular afferent receptors are modified both electrophysiologically as well as histologically during states of chronic cardiac enlargement will be investigated initially. Alterations in the reflex control of the circulatory system will be investigated in normal and heart failure animals by stimulation of discrete receptor populations. The mechanism(s) responsible for altered reflex control will be investigated by observing such parameters as intracardiac pres ures, diameter, blood vessel diameter, etc. Alterations in renal function and renal nerve activity will also be investigated.